The present invention relates to a device for pushing away an enclosure arranged around a dental element, in order to produce a space which is to be filled with filling material between the said enclosure and the dental element, said device comprising a handle part, the end being provided with a thickened section for engaging on the said enclosure.
A dental tool of this type is known from U.S. Pat. No. 5,947,731A. When molars or other dental elements are being filled, it is common to use matrix bands which are placed around the element in question. The space between the matrix band and the dental element is then filled with filling material, such as (white) plastic-based filling material.
In this operation, it is important for the repaired dental element to rest as tightly as possible against adjacent dental elements, since if a gap forms between two dental elements, in the vicinity of the free end thereof, food and the like can accumulate between them, leading to caries and parodontitis.
Therefore, it is important for the matrix band to be arranged so that it bears as tightly as possible against adjacent dental elements.
U.S. Pat. No. 5,947,731A proposes a pliers-like tool with which a band of this type is pushed outwards during the filling operation, in order in this way to ensure that there is sufficient space for the filling material to be introduced.
In this case, firstly filling material, such as composite, is arranged in the opening which is to be filled and then the end of the pliers-like tool is introduced. After the band lying around the cavity has been pressed onto the adjacent dental element and the filling material has (partially) cured, the end of the pliers is removed. The impressions caused by the ends are finished using further filling material.
It has been found that in this way, although the object of optimum contact between the adjacent dental elements during the filling operation can be achieved, considerable stresses arise in the filling material. These stresses are dependent on the material used and, when composite material is used, will primarily be shrinkage stresses. As a result, the service life of fillings of this type is considerably restricted.
The object of the present invention is to provide a device for pushing away an enclosure arranged around a dental element, so that it is possible to avoid the above-described residual stresses in the filling material after it has cured.
In a device as described above, this object is achieved in that said thickened section is of oval design and, in the vicinity of the free end, approximately in the centre of the longest side thereof, is provided with a recess.
More particularly, said recess is wave shaped and has a length of between 0.5 and 5 mm, more particularly between 1 and 3 mm.
As a result of the presence of a recess, a mirror-image protrusion which is delimited by a recess defined by the end of the thickened section is formed in the filling material on both sides after (partial) curing. As a result, two adjacent compartments which are separated by the protrusion are formed. Surprisingly, it has been found that as a result the effect of shrinkage of, for example, a composite filling material is avoided. The shape described above allows shrinkage to be guided away to the outside.
At the location of the protrusion there is no contact with the walls and the shrinkage can occur freely. The remainder of the shrinkage is guided away to the outside, onto the walls. The fact that the instrument or outlet part is left in position during the exposure means that a shadow effect also occurs during the exposure. The layer which is against the walls receives most light and cures first. The layer which is remote from the walls, beneath the instrument or filling tip, will harden later and will therefore shrink towards the walls. The shadow effect simulates, as it were, a layered filling, which also has a positive effect on shrinkage stress on the walls. The residual shrinkage stress on the walls is therefore negligible.
The device described above can be used in any device for pushing away a dental element, i.e. a thickened section with a recess as described above can be used in a pliers-like tool but also in “single” tools which comprise only one thickened section, in which case the contact with the adjacent dental element has to be applied by pressure from the person making the filling.
A construction of this type can be combined, for example, with an outlet part.
Outlet parts for use on dental composite syringes are known from the prior art. Known outlet parts comprise an exchangeable plastic part which functions as the syringe nozzle and is arranged on a composite syringe. With the known outlet parts, a liquid composite material is arranged in a prepared dental element, after which the composite is pressed on and moulded by means of another tool.